This is maybe a very stupid question but it has always been in the back of my mind.  And now that I have added several new disks to my newly re-built array I'm thinking about it again.  Is there any disadvantage (or advantage) to having several really full disks and several really empty disks...?  As most of us I have grown my array over time and the result of that is that 4-5 of my disks are nearly 100% full, I then have another 5 or so that are less that 25% full and then the new group of 4 that are totally empty (or close to it).  Should I move some of the data from the very full drives over to some of the empty ones.

 

Said another way, is there any advantage to spreading all my data across all my drives so that each drive is about the same fullness..?

 

If this was a really dumb question just tell me so...

Writing to any drive is fastest starting out and slower as it gets filled up.

If you fill up drives and then start on the next drive I would think you get to experience the thrill (haha) of having a fast drive over again.  As opposed to filling all up equally then the system would over time become slower and slower. 

 

The lazy man says fill up drives and add new ones because who wants to do maintenance anyway?

 

However, there is one gotcha.  You should leave a little bit of free space on every drive.  The reason for this is that ReiserFS (which is unRAID's file system) is a journaled file system.  This means that it can replay journaled transactions and potentially help you save data after a catastrophic event such as a power loss.  However, the drive needs free space in order to replay these transactions.  The amount of free space you leave depends on what kind of files you store on your server.  The rule of thumb is that you leave at least as much free space as your single largest file.

 

For example:

If you store a lot of HD movies on a drive that are all around 8 GB in size, then you should leave 8 GB of free space on that drive.

If you store BD ISOs that are 50 GB each on a drive, then you should leave 50 GB of free space on that drive.

 

Depending on the size of your drives, unMenu will still likely show your drive as being 99% or 100% full even with this little bit of free space on it.

 

Finally, the 'fill up' disk allocation method has some reported problems or bugs.  I would recommend against using it for now.  Use 'high-water' instead.

 

Also finally, if you use a cache drive then the slowdown over time that queeg mentioned will be completely invisible to you.